I was reading Title 21 of the Code of Federal Regulations when I came upon the following sentence

(n) The inactive ingredients when a safety factor, or reference to an enclosed circular containing appropriate information;

How is it determined if an inactive ingredient is a safety factor?

  • To potential answerers: I won’t be accepting either answer as neither truly conclusively answers the question. Commented May 27, 2019 at 5:37

2 Answers 2


A partial answer (for a manufacturer) is "look it up" – that may tell you if a determination has been made by the FDA. If so, it is not new and

may require a less extensive review the next time it is included in a new drug product. For example, if a particular inactive ingredient has been approved in a certain dosage form at a certain potency, a sponsor could consider it safe for use in a similar manner for a similar type of product

(the FDA says). The legal part doesn't explain how it is scientifically determine that an inactive ingredient raises safety concerns but to take on example, wheat gluten is in the Inactive Ingredient Guide. This article gives a bit of analysis of the factors that sponsors have to consider in shouldering their burden of proof. If you want to manufacture a new vaccine, you have to show (the FDA) that it is safe. If you dilute the vaccine with water, that ingredient is not a "safety factor". Benzalkonium chloride could be (you would have to show that it isn't), and if it is, that regulation requires you to list it. What's not specified clearly is how many adverse reactions per million doses constitute being a safety factor.

  • The safety part is generalized. It just refers to things a broad portion of people would be allergic to or not want for some reason.
    – Putvi
    Commented May 6, 2019 at 23:18
  • I am not criticizing your answer, I just meant it's not a specific number and probably couldn't be since everyone is different.
    – Putvi
    Commented May 6, 2019 at 23:21
  • Are you saying all inactive ingredients must be listed unless it appears in the database? Commented May 6, 2019 at 23:26
  • 1
    No, that they must be listed if they are deemed to be a "safety factor", pursuant to the FDA review. The FDA has authority to make that determination, and the law doesn't specify precise steps whereby they make that determination.
    – user6726
    Commented May 6, 2019 at 23:52
  • Ah OK, so all inactive ingredients must be listed unless the FDA says it is safe and it doesn't. If it is in that database, it must be listed. Is that correct? Commented May 7, 2019 at 1:20

It means you list what is in the drug.

"Every drug manufacturer is obliged to list every excipient, every little part including coloring and flavors for each drug," says Andrzej Wilk, PhD, senior scientific liaison to USP's Nomenclature, Safety and Labeling Expert Committee. "This can be found on the package of a prescription drug or in the drug's package insert. For over-the-counter drugs, inactive ingredients have to be on the outside of the box."https://www.consumerreports.org/cro/news/2012/03/q-a-how-can-i-find-out-which-ingredients-are-in-a-medication/index.htm

If you have some special case where you can not have a specific chemical, you either ask the pharmacist or read the info yourself to decide if it is a safety risk for you.

  • Sorry if I didn't make this clearer. I am interested in vaccines. In the FDA, drugs and biologics are different. Commented May 6, 2019 at 20:59
  • 1
    A vaccine is a drug.
    – Putvi
    Commented May 6, 2019 at 21:00
  • I don't want to go into a lot of detail over this. The division of the FDA responsible for overseeing drugs is CDER. For biologics, it is CBER. In general terms, drugs are not derived from human, animal, or plant tissue whereas biologics are. They are distinctly different according to the FDA including in regulation. Commented May 6, 2019 at 21:02
  • 1
    Thats fine that they have different categories, but the requirement to list what is in them is the same. They even make a PDF of what is in each vaccine. cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/B/…
    – Putvi
    Commented May 6, 2019 at 21:03
  • 1
    Yeah, I get you. I just meant you are bolding the when a safety factor like it only says when a safety factor and ignoring the rest of the sentence.
    – Putvi
    Commented May 6, 2019 at 21:16

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